<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>网站首页</title>
</head>
<body>
    <style>
        div{
            width: 99vw;
            height: 98vh;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        span{
            font-size: 50px;
            color: red;
        }
    </style>

    <div>
        <span></span>
    </div>
</body>
</html>